The present invention relates to a transmitting device, a receiving device and a contents transmitting method suitable to protect copyrights of contents to be transferred, when information, such as contents which include images and sound, is transmitted and received via a network.
With the growth of the processing power such as computing speed and storage capacity of personal computers (hereafter referred to as PC), there has been a significant increase in the capacity of the hard disc drives (hereafter referred to as HDD) mounted in the PC. Under the circumstances, even with PCs of levels for general household use, it has become possible to record TV programs and watch them on the PC screen.
Meanwhile, in the trend of lowering price of large-capacity HDDs, HDD-mounted video recording equipment for household use came on to the market, which has a built-in HDD and digitally records video and audio information, and its improved usability owing to use of discs as recording media has been drawing attention.
In HDD-mounted video recording equipment and PCs for video recording as mentioned above, information such as images and sound is recorded in the HDD fixed in the system. Therefore, when a user wants to watch the recorded program in another place in the house, it is necessary to convey the whole HDD-mounted equipment to another place. For this reason, the difficulty has been felt in realizing the portability of HDD video recorders unlike with the VTR recorders which provide the excellent portability of audio-visual information on medium level; moreover, a number of VTR recording/playback units using replaceable media can be provided at a less-expensive cost.
Therefore, it has been contemplated to make it possible to play back audio-visual information anywhere in one's house by mounting an interface to wired/wireless LAN (Local Area Network) in the video recorder and transmitting signals over a network to another PC or receiving device.
As means for protecting copyrights of information, such as contents, there is the Digital Transmission Content Protection (DTCP) specification which defines a cryptographic protocol for protection on digital buses of the IEEE 1394 standard as described in “5C Digital Transmission Content Protection White Paper” by five companies including Hitachi, Ltd., et al., which is an example of the method for protecting illegal copying and the like on digital AV devices.
A number of techniques have been disclosed to realize protection from illegal copying, intercepting and tampering to thereby protect copyrights as information traverses between devices or between networks, two examples of which are disclosed in JP-A-2000-287192 and JP-A-2001-358706.
In the prior art mentioned above, more specifically, in a case where an interface to wired/wireless LAN is mounted in a home video recorder, and a content is transmitted to another PC or receiving device via a network to enable visual-audio information to be reproduced anywhere in the house, consideration has not be taken about protection of copyrights of visual-audio information (hereafter referred to as content) which should receive copyright protection, and visual-audio information recorded in the HDD could further be stored in the HDD in another PC that received the information via a LAN, and visual-audio information that could be handled had to be “copy-freely” content which was freely copyable.
When a digitally recorded content is transmitted from one device to another via a network as mentioned above, data being transferred is less susceptible to quality deterioration and a copy (duplicate) of the same quality as the content in the device on the transmitter side can generally be produced on the receiver's side. Therefore, it is necessary to take consideration for the prevention of illegal copying of content that deviates from the range of personal use to visual or audio data (hereafter referred to as content) the copyright of which should be protected. For example, when a content is transmitted between AV devices, the content is encrypted on the content transmitting device's side, and information for decryption is shared with the receiving device's side in order to prevent the content from being correctly received and decrypted by any device other than the content receiving device as the legitimate destination, by which copy protect is implemented to thereby prevent unrestricted copying.
An example of copy protect method adopted in digital AV devices is the DTCP method described in 5C Digital Transmission Content Protection White Paper. In the DTCP method, contents are classified into “copy-freely”, “copy-one-generation”, and “copy-never” contents and managed accordingly, and the video recorder records only “copy-freely” and “one-copy-generation” contents, and treats the “copy-one-generation” content which it has recorded once as a “no-more-copies” content, and the contents are subjected to an encryption process on the transmitter side except for “copy-freely” contents and transmitted on the buses, thereby preventing unrestricted copying of contents.
Also for transmission on a wired or wireless LAN, there have been disclosed some techniques, based on a similar viewpoint as in the DTCP method, for realizing the copy protect to protect copyrights. For example, JP-A-2000-287192 discloses a technique for applying a method similar to DTCP to a copy protect system in distribution of digital contents on the network, and likewise JP-A-2001-35706 discloses a technique for making a configuration between devices which communicate contents in encrypted form for copyright protection.
In these, no consideration is taken as to whether the transmitter and the receiver are located within a same house when contents are transmitted via a wired or wireless LAN. In a case where content is downloaded from a distribution server, it is quite usual that the transmitter side is in a provider site and the receiver side is in the house of user, for example.
Therefore, when some one is going to record a content by the HDD of a PC or a HDD video recorder and transmit to another device in the family, assuming that the above-mentioned technique is used, if the LAN in the family is connected to the Internet, the content can be received by the receiving devices located in other families connected via the Internet, and can be displayed on the monitor screens, and the range of communication extends to any places throughout the world so long as they are connected to the Internet.
Under the present state of affairs, even if one wants to carry out copy protect by the above techniques, when the user of the video recorder makes the video recorder accessible through the Internet, any receiving device furnished with the above-mentioned copy protect function can receive content and the content can be displayed on the screen, resulting in a great deviation from the range for personal use, which is the intended purpose of copyright protection.